Control for arc lamps



Nov. 28, 1939.

F. C. COATES CONTROL FOR ABC LAMPS Filed Aug. 27, 1958 mu Y mm Wm Z Co a 6 W m M Patented Nov. 28, 1939 UNITED STATES PATENT OFFICE CONTROL FOR ARC LAluPS Application August 27, 1938, Serial No. 227,141 In Great Britain August 17, 1938 10 Claims.

My invention relates to electric arc lamps and has particular reference to an improved system for controlling the feeding of the several sets of carbon electrodes employed in lamps using single sets, twin sets, or a plurality of sets of electrodes in a single circuit.

In carbon electrode arc lamps it is desirable to maintain the arc length as nearly at a constant value as possible to maintain a uniform degree of brilliance of illumination therefrom and to maintain the quality of the light produced by the arc. The constancy of the quality and quantity .of light from an arc lamp is very important in certain types of work, such as the lighting of motion picture sets, especially those used in color photography work.

It has been found, however, that while the maintenance of arc length is an important factor in controlling the light out-put of an arc lamp, certain other disadvantages arise which are not solved by the use of a feeding mechanism of this type; for example, if the current used in the arc is caused to flow through the arc in a direction opposite to that for which the lamp is designed, the lamp operates improperly due to the fact that the crater is formed on the wrong electrode and the carbons burn improperly since thepositive and negative carbons are usually of different composition.

It has also been found that electrode feeding mechanisms which operate to maintain the length of arc at a substantially constant value will continue in their operation until the feeding mechanism has reached the limit of its control range. Unless this condition is perceived by an operator of the lamp, the feeding mechanism will remain in an energized condition and be subjected to unusual load conditions which may well result in permanent damage.

It is therefore a primary object of my invention to provide a control circuit for arc lamps wherein, upon the consumption of the electrodes of any of the arcs to a predetermined value, the feeding devices for all of the arcs will be automatically disconnected.

It is another object of my invention to provide a control circuit for arc lamps wherein current may flow through the arcs in one direction but not in a reversed direction.

It is an additional object of my invention to provide a single mechanism which will accomplish the above objects.

Other objects and advantages of my invention will be apparent from a study of the following specification, read in connection with the accompanying drawing, wherein The figure is a diagrammatic view illustrating a twin arc lamp complete with feeding mechanism for feeding the electrodes thereof, power circuits for the arcs, and control circuits for the feeding mechanism, together with the mechanism and circuits for limiting the operation of the feeding mechanism.

While it will be understood by those skilled in this art that my control mechanism may be applied to any type of arc lamp which includes an automatic or power actuated feeding mechanism for moving the electrodes toward each other as they are consumed, I have illustrated one embodiment of my invention herein as applied to a twin arc lamp of the general character disclosed and claimed in my copending application Serial No. 201,550, filed April 12, 1938. The twin arc lamp illustrated herein may comprise a pair of arcs to be associated with each other and operated together as twin arcs A and B. Each of the arcs is drawn between a pair of electrodes, the are A including a positive electrode Al and a negative electrode A2. Each of these electrodes is carried in suitable electrode holders A3 and A4, respectively, suitable insulating bushings 3 and 4 being interposed between the electrodes and the holders to electrically insulate the holders.

The holders are adapted to be moved toward and away from each other to feed the electrodes during the striking of the arc and the consumption of electrodes while the arc is burning, such feeding operation being accomplished by means of any suitable power mechanism illustrated herein as an electric motor diagrammatically shown as having its armature A5 connected to both of the electrode holders A3 and A4 by means of a pinion A-6 engaging gear racks A1 and A8 formed upon or associated with the electrode holders A3 and A4, respectively.

In like manner the arc B includes electrodes 3-! and B-2 carried by electrode holders B-3 and B-4 and insulated therefrom by insulating bushings 5 and 6. The holders are adapted to be 4 operated in a manner similar to that which has just been described with respect to the are A by a feeding motor armature 3-5.

The are circuit includes main line conductors L-l and L2 which are suitably connected to an attaching plug 9. In operation the are current flows from the conductor L-l through a wire I0 to the electrode Al, thence to the electrode A2 and through a wire II toa ballast resistor 12. From the ballast resistor 12 the curarc, will cause a potential to appear across the,

armature terminals of the motor A-5 in such a direction as to cause the feeding mechanism to bring the arc electrodes closer together. One

side of the bridge circuit for the are A includes a control potentiometer AR which is connected in the circuit in such manner that the main line conductor L-i is attached to one end of the resistance element and the other end of the resistance element is connected by means of a conductor I5 to the arc circuit at a point common to the ballast resistor 52 and the electrode B! of the arc B.

The other side of the bridge circuit includes the are A and the ballast resistor I2. The motor armature A-5 for controlling the are feeding mechanism is connected by means of conductor 88 to the movable arm portion of the potentiometer AR and by means of a conductor ll to a point in the arc circuit common to the ballast resistor 12 and the electrode A-2 of the arc A.

The control circuit for the motor B-'.i of the feeding mechanism for the arc B is similar to that just described and includes a control potentiometer BR forming one side of a bridge circuit through its connection to the main line conductor L-2 at one end of the resistance element and by a conductor !8 connecting the other end of said resistance element to a point in the arc circuit common to the ballast resistor l2 and the electrode A-2 of the are A.

As in the case of the are A, the ballast resistor l2 forms the other side of the bridge circuit for controlling the feeding motor B-5. The motor 13-5 is connected by means of a conductor 19 to the movable arm portion of the potentiometer BR and by means of a conductor 20 to a point in the arc circuit common to the ballast resistor I2 and the electrode B-l of the arc B.

Field windings AF and BF associated with the motor armatures A5 and B5 respectively, are preferably connected in series with each other and with a current limiting resistor R, the series circuit extending between the main line conductors L-l and L-2. The motor field windings AF and BF and the resistor R are so proportioned as to insure sensitive response of the feeding mechanism to small currents passing through the motor armatures.

In operation the electrodes of the arcs continually burn away and the feeding mechanism brings the arc supports, A-3 and A---@ for example, in the case of the are A, closer and closer together until the limit of control of the feeding mechanism is reached. As has been previously stated, it is desirable that both feeding motors be disconnected when this condition occurs. I have provided in this invention a mechanism for accomplishing this, which may be readily applied to the arc lamp just described.

This mechanism includes a bar 4| which extends immediately below both of the gear racks Al and 13-3 of the are feeding apparatus for both arcs A and B. The bar M is normally located in such a position as to be engaged by either of the descending gear racks when they have been moved downwardly to the limit of the feeding motion of the electrodes for the associated arc.

The bar ll is illustrated as being mounted upon a pivoted armature 42 of the polarized relay 43 (the purpose of which will be hereinafter decribed), the armature and bar being normally urged upwardly by means of a spring 44 which may, for convenience, be interposed between a permanent magnet 45 of the relay and a downwardly extending tail piece 46 on the armature 42. The bar M carries a pair of switch contacts i l--41 and B- l'l arranged to be normally urged into contacting relation with corresponding switch contacts A-4i8 and 13-48 respectively. The contacts A- il and A--% are interposed in the conductor It, leading to the feed motor armature A5, while the contacts 13-41 and B-48 are interposed in the conductor l9 leading to the feed motor armature B-ii.

Thus, when the electrodes A! and A2 for the are A have been fed toward each other until the electrodes have been substantially consumed, the lower end of the gear rack A'l will engage the switch bar ll and move it downwardly, operating to disengage both of the contacts A-dl and B -d? from their corresponding contacts A di; and B--48, and prevent downward feeding of either of the sets of electrodes, thus preventing either of the feed motors from further attempting to bring its associated electrodes toward each other.

As has been previously pointed out, it is desirable that the attaching plug 9 be connected to the source of electric current supply in such a manner as to cause the current to flow through the arcs in but one of the two possible directions. For this purpose I have illustrated the polarized relay 43 as having its coil 49 connected across the lines L-l and L-2 as by conductors 50 and El, the permanent magnet 45 of such relay being arranged in such a manner that when the lines Ll and L-Z are connected to the proper polarities for causing current to flow through the arcs in the desired direction the relay armature 42 will be unaffected, but if the connection of lines L! and L-2 is reversed, the relay armature will be drawn downwardly, breaking the feeding motor armature circuits at the contacts A- l'l, A-At and B-M', 3-48 to prevent the striking of the arcs.

It is readily seen that in case it is desired to apply this limit mechanism to a plural arc lamp utilizing more than two arcs, the bar 4| may be moved to the rear sufficiently to allow it to be extended beyond the gear racks of the feeding mechanisms for intermediately located arcs so as to lie in close proximity to the feeding mechanism of each of the multiplicity of the arcs. Suitable projections would be provided on gear racks corresponding to the racks illustrated as A-'i and B fl, the projections extending rearwardly sufficiently far to engage the extended bar 4|. The bar 4| would of course be fitted with as many contacts, similar to contacts A-4T and A48, as there are feeding mechanisms for the. arcs, each contact mechanism being included in the circuit for the feeding motors.

It will be observed that I have provided an improvement for arc feeding mechanisms as of such type to prevent the arc lamps so equipped from being used with the electrode polarities reversed, and which will also operate to prevent continued operation of the are feeding motors after the feeding mechanism has reached the limit of its control range.

While I have shown and described the preferred embodiment of my invention, I do not desire to be limited to any of the details of construction shown or described herein, except as defined in the appended claims.

I claim:

1. In a system for controlling the feeding of electrodes of an arc lamp, the combination of: a pair of electrodes connected across a supply line and forming an arc; an electrode holder for each electrode; an electromotive feeding means coupled to said pair of electrode holders and operable to move said holders toward each other; a circuit connecting said feeding means to said supply line to supply power for the operation thereof; normally closed switch means interposed in said circuit for said feeding means; and polarized relay means connected across said are and coupled to said switch means for opening said switch means when said are is supplied with current of a predetermined polarity from said supply line.

2. In a system for controlling the feeding of electrodes of an arc lamp, the combination of a pair of electrodes connected across a supply line and forming an arc; an electrode holder for each electrode; an electromotive feeding means coupled to said pair of electrode holders and operable to move said holders toward each other; a circuit connecting said feeding means to said supply line to supply power for the operation thereof; switch means interposed in the circuit for said feeding means; means extending in the path of movement of one of said electrode holders to be engaged thereby when said holders have been moved toward each other to a predetermined position for opening said switch means; and polarized relay means connected across said arc and coupled to said switch means for opening said switch means when said are is supplied with current of a predetermined polarity from said supply line.

3. In a system for controlling the feeding of electrodes of a plural arc lamp, the combination of a plurality of pairs of electrodes forming a plurality of arcs, one for each pair of electrodes, connected for simultaneous operation; an electrode holder for each electrode; an electromotive feeding means for each are coupled to the associated pair of electrode holders and operable to move said holders toward each other; a circuit for each of said feeding means to supply power for the simultaneous operation thereof; and a single means extending in the path of movement of said electrode holders for all of said arcs to be engaged thereby when any pair of said holders has been moved toward each other to a predetermined position for interrupting all of said circuits for all of said feeding means.

4. In a system for controlling the feeding of electrodes of a plural arc lamp, the combination of: a plurality of pairs of electrodes forming a plurality of arcs, one for each pair of electrodes; an electrode holder for each electrode having a gear rack portion; an electric motor feeding means for each arc having a pinion engaging the associated pair of gear racks and operable to move said holders toward each other; a circuit for each of said electric motor feeding means to supply power for the operation thereof; and switch means engageable by at least one of said gear racks in response to the movement of said holders toward each other to a predetermined position for interrupting all of said circuits for all of said electric motor feeding means.

5. In a system for controlling the feeding of electrodes of a plural arc lamp, the combination of a plurality of pairs of electrodes forming a plurality of arcs, one for each pair of electrodes; an electrode holder for each electrode; an electromotive feeding means for each are coupled to the associated pair of electrode holders and operable to move said holders toward each other; a circuit for each of said feeding means to supply power for the operation thereof; switch means interposed in the circuits for all of said electromotive feeding means; and means extending in the path of movement of the electrode holders for all of said arcs to be engaged thereby when any pair of said holders has been moved toward each other to a predetermined position for opening all of said switch means.

6. In a system for controlling the feeding of electrodes of a plural arc lamp, the combination of: a plurality of pairs of electrodes connected to a power supply line and forming a plurality of arcs, one for each pair of electrodes; an electrode holder for each electrode; electromotive feeding means for each arc coupled to the associated pair of electrode holders and operable to move said holders toward each other; circuit means connecting each of said electromotive feeding means to said supply line; normally closed switch means interposed in said circuit means for said feeding means; and polarized relay means connected across said arcs and coupled to said switch means for opening said switch means when said arcs are supplied with a current of a predetermined polarity from said supply line.

7. In a system for controlling the feeding of electrodes of a plural arc lamp, the combination of a plurality of pairs of electrodes connected across a supply line and forming a plurality of arcs, one for each pair of electrodes; an electrode holder for each electrode; an electromotive feeding means for each are coupled to the associated pair of electrode holders and operable to move said holders toward each other; circuit means connecting each of said feeding means to said supply line; switch means interposed in said circuit means; means extending in the path of movement of said electrode holders for all of said arcs to be engaged thereby when any pair of said holders has been moved toward each other to a predetermined position for opening all of said switch means; and polarized relay means connected across said arcs and coupled to said switch means for opening said switch means when said arcs are supplied with current of a predetermined polarity from said supply line.

8. In a system for so controlling the feeding of electrodes in a plurality of series connected arcs as to maintain the length of each of said arcs at a substantially constant value, the combination of: an arc circuit extending across a supply line including a plurality of pairs of electrodes connected in series relation with each other to comprise a plurality of arcs; a pair of electrode holders for each of said pairs of electrodes; an auxiliary circuit connected across the supply line and having selected resistance portions therein associated respectively with each of said arcs; individual electromotive feeding means for moving each pair of electrode holders toward each other; circuit means connecting the feeding means for each arc to the arc circuit between the associated arc and the next adjacent arc and to the auxiliary circuit between the resistance portion for the associated arc and the resistance portion for the remaining arcs, and means for interrupting all of said circuit means for said feeding means extending in the path of movement of said electrode holders for all of said arcs.

9. In a system for so controlling the feeding of electrodes in a plurality of series connected arcs as to maintain the length of each of said arcs at a substantially constant value, the combination of: an arc circuit extending across a supply line including a plurality of pairs of electrodes connected in series relation with each other to comprise a plurality of arcs; a pair of electrode holders for each of said pairs of electrodes; an auxiliary circuit connected across the supply line and having selected resistance portions therein associated respectively with each of said arcs; individual electromotive feeding means for moving each pair of electrode holders toward each other; circuit means connecting the feeding means for each arc to the arc circuit between the associated arc the next adjacent arc and to the auxiliary circuit between the resistance portion for the associated arc and the resistance portion for the remaining arcs; normally closed switch means included in said circuit means for said feeding means; and polarized relay means connected across said arcs and coupled to said switch means.

10. In a system for so controlling the feeding of electrodes in a plurality of series connected arcs as to maintain the length of each of said arcs at a substantially constant value, the combination of: an arc circuit extending across a supply line including a plurality of pairs of electrodes connected in series relation with each other to comprise a plurality of arcs; a pair of electrode holders for each of said pairs of electrodes; an auxiliary circuit connected across the supply line and having selected resistance portions therein associated respectively with each of said arcs; individual electromotive feeding means for moving each pair of electrode holders toward each other; circuit means connecting the feeding means for each arc to the arc circuit between the associated arc and the next adjacent arc and to the auxiliary circuit between the resistance portion for the associated arc and the resistance portion for the remaining arcs; switch means included in said circuit means; means extending in the path of movement of said electrode holders for all of said arcs; and polarized relay means connected across said arcs and coupled to said switch means.

FIELDING C. COATES. 

